We report here the additive Runge-Kutta methods for computing reactive Euler equations with a stiff source term, and in particular, their applications in gaseous detonation simulations. The source term in gaseous detonation is stiff due to the presence of wide range of time scales during thermal-chemical non-equilibrium reactive processes and some of these time scales are much smaller than that of hydrodynamic flow. The high order, L-stable, additive Runge-Kutta methods proposed in this paper resolved the stiff source term into the stiff part and non-stiff part, in which the stiff part was solved implicitly while the non-stiff part was handled explicitly. The proposed method was successfully applied to simulating the gaseous detonation in a stoichiometric H 2 /O 2 /Ar mixture based on a detailed elementary chemical reaction model comprised of 9 species and 19 elementary reactions. The results showed that the stiffly accurate additive Runge-Kutta methods can capture the discontinuity well, and describe the detonation complex wave configurations accurately such as the triple wave structure and cellular pattern. Reacting flows, specifically in gaseous combustion, have been a significant topic of active research for more than one hundred years. The strong coupling between hydrodynamic flow and chemical kinetics is complex and even today many phenomena are not very well understood yet. Gaseous detonation is a process of supersonic combustion in which a shock wave is propagated and supported by the energy release in a reaction zone behind it. It is the more powerful and destructive of the two general classes of combustion, the other one being deflagration. The primary difficulty in computing reacting flows is the source term stiffness inherent in the reactive Euler equations in temporal integrations. Besides, the viscous stress and heat flux terms in the boundary layers can cause the stiffness too. The source terms are stiff because the thermal-chemical non-equilibrium reactive processes possess a wide range of time scales and some of them are much smaller than that of hydrodynamic flow [1]. The simulation will be inefficient when the explicit methods rather than the implicit methods are used, because the time-step sizes dictated by the stability restraint in explicit methods are much smaller than those required by the CFL condition. Due to these limitations in explicit methods, the implicit methods are normally required to simulate gaseous detonation. The practical implicit methods for gaseous detonation simulation can be categorized into two classes, i.e. the time-splitting method and the additive semi-implicit method [2,3].The time-splitting methods [4][5][6][7][8], resolve the source term of reactive Euler equations into ( ) ( ), t